Object:
To study the effect of osmolarily of salt solutions and haemolytie agents on red blood corpuscles
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Requirements:
Test-tubes, sodium chloride solutions of different percentage, ether or benzene or chloroform and potassium hydroxide.
Principle and procedure:
Erythrocytes are membranous envelopes filled with haemoglobin. The envelope or plasma membrane is semipermeable, hence substances in solution can pass in and out of the corpuscle.
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If normal red blood corpuscles are placed in normal sodium chloride solution which has the same concentration as the contents of the corpuscles, then no exchange takes place because the osmotic pressure of corpuscles and of the saline solution is the same.
The salt solution is said to be isotonic or of equal- concentration with the corpuscles. If normal red blood corpuscles are put in a dilute solution of sodium chloride, they absorb water from the salt solution, and they swell up, become spherical, and finally rupture.
The ditute salt solution is hypotonic because its osmotic pressure is lower than that of the interior of the corpuscles.
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If normal red corpuscles are placed in strong salt solution in which the concentration of sodium chloride is higher than in the red corpuscles, then the corpuscles shrink and become wrinkled.
The strong salt solution is hypertonic because its osmotic pressure is greater than that of the interior of the eorpuscles and the fluid passes from the corpuscles into the salt solution.
A. Put 1 ml of venous blood in each of three small test-tubes. To the first tube add 1 nil of 0 85% sodium chloride solutions (isotonic).
To the second tube add 1 ml of 0–5% sodium chloride solution (hypotonic). “To the third tube add 1 ml of l–5% sodium chloride solution (hypertonic). Shake the tubes and note the results.
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In a hypotonic solution the red corpuscles rupture, in rupturing the haemoglobin passes from the red corpuscles into the plasma, the plasma becomes red in colour.
This is called haemolysis or taking of biood. The substances inducing haemolysis are called haemolytic agents.
Some common haemolytic agents are hypotonic solutions, fat solvents, snake venoms, and some toxins.
B. Take a drop of blood in a test-tube, add a fat solvent (such as ether, benzene, chloroform or bile salts), shake the tube, the blood will be haemolysed because the fat component of the plasma membrane of red corpuscles is dissolved and haemoglogin is set free.
C. Take a drop of blood in a test-tube, and a few drops of 0 2% potassium hydroxide, the red corpuscles are dissolved.